package com.example.demo;

import java.math.BigDecimal;
import java.util.*;
import java.util.stream.Collectors;

import static java.util.Comparator.comparingLong;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toCollection;

/**
 * @author yishuangshuang
 * @ClassName: Apple
 * @Description: TODO
 * @date 2019/1/3 11:00 AM
 */
public class Apple {
    private Integer id;
    private String name;
    private BigDecimal money;
    private Integer num;

    public Apple(Integer id, String name, BigDecimal money, Integer num) {
        this.id = id;
        this.name = name;
        this.money = money;
        this.num = num;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public BigDecimal getMoney() {
        return money;
    }

    public void setMoney(BigDecimal money) {
        this.money = money;
    }

    public Integer getNum() {
        return num;
    }

    public void setNum(Integer num) {
        this.num = num;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("Apple{");
        sb.append("id=").append(id);
        sb.append(", name='").append(name).append('\'');
        sb.append(", money=").append(money);
        sb.append(", num=").append(num);
        sb.append('}');
        return sb.toString();
    }

    public static void main(String[] args) {
        List<Apple> appleList = new ArrayList<>();//存放apple对象集合

        Apple apple1 = new Apple(1, "苹果1", new BigDecimal("3.25"), 10);
        Apple apple12 = new Apple(1, "苹果2", new BigDecimal("1.35"), 20);
        Apple apple2 = new Apple(2, "香蕉", new BigDecimal("2.89"), 30);
        Apple apple3 = new Apple(3, "荔枝", new BigDecimal("9.99"), 40);

        appleList.add(apple1);
        appleList.add(apple12);
        appleList.add(apple2);
        appleList.add(apple3);

        //List 以ID分组 Map<Integer,List<Apple>>
        Map<Integer, List<Apple>> groupBy = appleList.stream().collect(Collectors.groupingBy(Apple::getId));
        System.err.println("groupBy:" + groupBy);

        /**
         * List -> Map
         * 需要注意的是：
         * toMap 如果集合对象有重复的key，会报错Duplicate key ....
         *  apple1,apple12的id都为1。
         *  可以用 (k1,k2)->k1 来设置，如果有重复的key,则保留key1,舍弃key2
         */
        Map<Integer, Apple> appleMap = appleList.stream().collect(Collectors.toMap(Apple::getId, a -> a, (k1, k2) -> k1));
        System.out.println("appleMap:" + appleMap);

        //过滤出符合条件的数据
        List<Apple> filterList = appleList.stream().filter(a -> a.getName().equals("香蕉")).collect(Collectors.toList());
        System.err.println("filterList:" + filterList);

        //计算 总金额
        BigDecimal totalMoney = appleList.stream().map(Apple::getMoney).reduce(BigDecimal.ZERO, BigDecimal::add);
        System.err.println("totalMoney:" + totalMoney);  //totalMoney:17.48

//        Optional<Apple> maxDish = Apple.menu.stream().
//                collect(Collectors.maxBy(Comparator.comparing(Apple::getMoney)));
//        maxDish.ifPresent(System.out::println);
//
//        Optional<Apple> minDish = Apple.menu.stream().
//                collect(Collectors.minBy(Comparator.comparing(Apple::getCalories)));
//        minDish.ifPresent(System.out::println);


        // 根据id去重
        List<Apple> unique = appleList.stream().collect(
                collectingAndThen(
                        toCollection(() -> new TreeSet<>(comparingLong(Apple::getId))), ArrayList::new)
        );
        System.out.println("unique:" + unique);

        System.out.println("appleList:" + appleList);


    }
}
